1. Field Of The Invention
The present invention relates generally to systems for separating multi-phase fluid streams, and more particularly, but not by way of limitation, to a system for separating oil, water and gas from a production stream of a well when the stream is subject to fluid slugging and/or external motion.
2. Brief Description Of The Prior Art
The typical prior art system used for three-phase separation is a single, large, horizontal or vertical vessel.
There are several commonly encountered situations which greatly increase the difficulty of satisfactorily separating gas, oil and liquid from such a production stream. One situation is where high gas-to-liquid ratios are encountered. The second situation is where flow-induced surging is encountered. The third situation is where motion-induced surging is encountered, typically on offshore floating platforms.
When high gas-to-liquid ratios are expected, typically a larger vessel will be used with a lower liquid operating level.
When flow-induced surging is expected, it is typically accommodated by installing vessels larger than that which would otherwise be dictated by the nominal production rate. The peak surge rate becomes the sizing criteria. Such large separators extract high penalties in the cost of a larger vessel and the support structure. This is particularly troublesome in offshore production systems where fluid surging is common due to multi-phase flow lines and risers, and where deck space is at a premium. In many situations involving fluid slugging, even the larger separators are not able to produce good oil and water qualities. Fluid slugs produce such extreme flow acceleration and deceleration in the vessel that good separation is virtually impossible.
When motion generated turbulence is a problem, such as on floating offshore production platforms, current separator design employs various components inside the separator to combat the effects of motion. For example, a system marketed by the CE Natco Company and generally known as the "Six Degree of Motion" separator design utilizes a "box" constructed within a horizontal vessel to compartmentalize the liquid.
Thus there is a need for a separating system of the smallest possible size and weight which is capable of providing good separation of gas, water and oil from a production fluid stream having high gas-to-liquid ratios and/or severe flow-induced fluid surging and/or significant motion-induced surging, all of which normally interfere with the efficient operation of typical prior art separating systems.